U.S. patent number 6,573,309 [Application Number 09/914,555] was granted by the patent office on 2003-06-03 for heat-curable, thermally expandable moulded park.
This patent grant is currently assigned to Henkel Teroson GmbH. Invention is credited to Xaver Muenz, Dirk Reitenbach.
United States Patent |
6,573,309 |
Reitenbach , et al. |
June 3, 2003 |
**Please see images for:
( Certificate of Correction ) ** |
Heat-curable, thermally expandable moulded park
Abstract
Foamable compositions which exhibit reduced surface tack and
better handling characteristics are obtained through the use of
specific combinations of epoxy resins. One or more solid epoxy
resins are utilized together with liquid and/or semi-solid epoxy
resins. The compositions, which preferably contain hollow glass
microspheres, are capable of providing foams which are useful in
the manufacture of reinforced structural members.
Inventors: |
Reitenbach; Dirk (St. Leon-Rot,
DE), Muenz; Xaver (Heidelberg, DE) |
Assignee: |
Henkel Teroson GmbH
(Heidelberg, DE)
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Family
ID: |
7899543 |
Appl.
No.: |
09/914,555 |
Filed: |
August 31, 2001 |
PCT
Filed: |
February 23, 2000 |
PCT No.: |
PCT/EP00/01474 |
PCT
Pub. No.: |
WO00/52086 |
PCT
Pub. Date: |
September 08, 2000 |
Foreign Application Priority Data
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Mar 3, 1999 [DE] |
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199 09 270 |
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Current U.S.
Class: |
521/135;
521/178 |
Current CPC
Class: |
C08G
59/186 (20130101); C08G 59/4021 (20130101); C08J
9/0061 (20130101); C08J 9/32 (20130101); C08J
2363/00 (20130101); C08J 2463/00 (20130101) |
Current International
Class: |
C08G
59/40 (20060101); C08J 9/32 (20060101); C08J
9/00 (20060101); C08G 59/00 (20060101); C08G
59/18 (20060101); C08J 009/02 () |
Field of
Search: |
;521/135,178 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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645735 |
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Jan 1994 |
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AU |
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0 798 062 |
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Oct 1997 |
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EP |
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10140125 |
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May 1998 |
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JP |
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WO86/00627 |
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Jan 1986 |
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WO |
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WO89/08678 |
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Sep 1989 |
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WO |
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WO93/00381 |
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Jan 1993 |
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WO |
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WO93/05103 |
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Mar 1993 |
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WO |
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WO95/21738 |
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Aug 1995 |
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WO |
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WO96/37400 |
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Nov 1996 |
|
WO |
|
WO97/19124 |
|
May 1997 |
|
WO |
|
WO98/15594 |
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Apr 1998 |
|
WO |
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WO98/52997 |
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Nov 1998 |
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WO |
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WO00/27920 |
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May 2000 |
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WO |
|
Other References
Glycidated Polybutadiene Diols As Epoxy Resin Modifiers, No. 416,
p. 5194, Research Disclosure, GB, Industrial Opportunities Ltd.,
Havant, Dec. 1998, XP000834080, ISSN:0374-4353..
|
Primary Examiner: Foelak; Morton
Attorney, Agent or Firm: Harper; Stephen D.
Claims
What is claimed is:
1. A thermosetting, thermally-expandable molded body comprising:
(a) at least one solid reactive resin selected from the group
consisting of (i) solid polyglycidyl ethers of polyphenols,
polyalcohols and diamines, (ii) solid polyglycidyl esters of
polycarboxylic acids, and mixtures thereof, (b) at least one liquid
reactive resin selected from the group consisting of (i) liquid
polyglycidyl ethers of polyphenols, polyalcohols and diamines, (ii)
liquid polyglycidyl esters of polycarboxylic acids, and mixtures
thereof, (c) at least one reactive resin conferring flexibility
selected from the group consisting of rubber-modified epoxy resins,
polyurethane-modified epoxy resins, adducts of amino-terminated
polyoxyalkylenes and polyepoxides, adducts of polymeric fatty acids
and epichlorohydrin, glycidol, or diglycidyl ethers of bisphenol A,
adducts of polyether polyols with epoxy resins,
polymercaptan-modified epoxy resins, polysulfide-modified epoxy
resins, and mixtures thereof, (d) at least one additive selected
from the group consisting of latent hardeners and accelerators, and
(e) at least one expanding agent.
2. A molded body as claimed in claim 1 wherein said molded body is
not tacky at room temperature.
3. A molded body as claimed in claim 1 wherein the solid reactive
resin (a) and the liquid reactive resin (b) are polyglycidyl ethers
of bisphenol A.
4. A molded body as claimed in claim 1 wherein the solid reactive
resin (a) has a melting point of from 45 to 90.degree. C.
5. A molded body as claimed in claim 1 wherein the solid reactive
resin (a) has an epoxy equivalent weight greater than 400.
6. A molded body as claimed in claim 1 wherein at least one
reactive resin conferring flexibility is an adduct of at least one
polymeric fatty acid and at least one diglycidyl ether of bisphenol
A.
7. A molded body as claimed in claim 1 wherein there is used as the
latent hardener dicyandiamide in an amount of up to 5 wt. %, based
on the total composition.
8. A molded body as claimed in claim 1 additionally comprising one
or more fillers, at least a part of the fillers being lightweight
fillers selected from the group consisting of hollow glass spheres,
flue ash, hollow plastic spheres, hollow ceramic spheres and
organic lightweight fillers of natural origin.
9. A molded body as claimed in claim 1 wherein the expanding agent
(e) is expandable hollow microspheres.
10. A molded body as claimed in claim 1 additionally comprising
fibers selected from the group consisting of aramide fibers, carbon
fibers, glass fibers, polyamide fibers, polyethylene fibers and
polyester fibers.
11. A molded body comprising: (a) one or more solid epoxy resins
selected from the group consisting of (i) solid polyglycidyl ethers
of polyphenols, polyalcohols, and diamines, (ii) solid polyglycidyl
esters of polycarboxylic acids, and mixtures thereof from 25 to 50
wt. % (b) one or more liquid epoxy resins selected from the group
consisting of (i) liquid polyglycidyl ethers of polyphenols,
polyalcohols, and diamines, (ii) liquid polyglycidyl esters of
polycarboxylic acids, and mixtures thereof from 10 to 50 wt. % (c)
one or more epoxy resins conferring flexibility selected from the
group consisting of rubber-modified epoxy resins,
polyurethane-modified epoxy resins, adducts of amino-terminated
polyoxyalkylenes and polyepoxides, adducts of polymeric fatty acids
and epichlorohydrin, glycidol, or diglycidyl ethers of bisphenol A,
adducts of polyether polyols with epoxy resins,
polymercaptan-modified epoxy resins, polysulfide-modified epoxy
resins, and mixtures thereof from 1 to 25 wt. %
12. A method of rigidifying and/or reinforcing a structure having a
hollow space, said method comprising: (i) molding a mixture
comprised of (a) at least one solid epoxy resin selected from the
group consisting of solid polyglycidyl ethers of polyphenols,
polyalcohols and diamines, solid polyglycidyl esters of
polycarboxylic acids, and mixtures thereof; (b) at least one liquid
epoxy resin selected from the group consisting of liquid
polyglycidyl ethers of polyphenols, polyalcohols and diamines,
liquid polyglycidyl esters of polycarboxylic acids, and mixtures
thereof; (c) at least one reactive resin conferring flexibility
selected from the group consisting of rubber-modified epoxy resins,
polyurethane-modified epoxy resins, adducts of polymeric fatty
acids and epichlorohydrin, glycidol, or diglycidyl ethers of
bisphenol A, adducts of polyether polyols with epoxy resins,
polymercaptan-modified epoxy resins, polysulfide-modified epoxy
resins and mixtures thereof; (d) at least one additive selected
from the group consisting of hardeners and accelerators; and (e) at
least one expanding agent; at a temperature of 60.degree. C. to
110.degree. C. to form a molded body; (ii) cooling the molded body;
(iii) introducing said molded body to said hollow space of said
structure; (iv) heating said molded body to a temperature of from
110.degree. C. to 200.degree. C., whereupon the volume of the
molded body expands and the molded body hardens to a thermoset.
13. A method as claimed in claim 12 wherein molding step (i) is
carried out by injection molding.
14. A method as claimed in claim 12 wherein molding step (i) is
carried out using a procedure selected from the group consisting of
extruding, casting, compression molding, and stamping.
15. A method as claimed in claim 12 wherein said molded body
expands in volume by from 50 to 100% during step (iv).
16. A method as claimed in claim 12 wherein the temperature in step
(i) is from 70.degree. C. to 90.degree. C.
17. A method as claimed in claim 12 wherein the temperature in step
(iv) is from 130.degree. C. to 180.degree. C.
18. A method as claimed in claim 12 wherein the molded body is
softened by heating when introducing the molded body to the hollow
space.
19. A method of rigidifying and/or reinforcing a substrate, said
method comprising: (i) molding a mixture comprised of (a) at least
one solid epoxy resin selected from the group consisting of solid
polyglycidyl ethers of polyphenols, polyalcohols and diamines,
solid polyglycidyl esters of polycarboxlic acids, and mixtures
thereof; (b) at least one liquid epoxy resin selected from the
group consisting of liquid polyglycidyl ethers of polyphenols,
polyalcohols and diamines, liquid polyglycidyl esters of
polycarboxylic acids, and mixtures thereof; (c) at least one
reactive resin conferring flexibility selected from the group
consisting of rubber-modified epoxy resins, polyurethane-modified
epoxy resins, adducts of amino-terminated polyoxyalkylenes and
polyepoxides, adducts of polymeric fatty acids and epichlorohydrin,
glycidol, or diglycidyl ethers of bisphenol A, adducts of polyether
polyols with epoxy resins, polymercaptan-modified epoxy resins,
polysulfide-modified epoxy resins and mixtures thereof; (d) at
least one additive selected from the group consisting of hardeners
and accelerators; and (e) at least one expanding agent; form a
molded body; (ii) cooling the molded body; (iii) applying said
molded body to said substrate; and (iv) heating said molded body to
a temperature of from 110.degree. C. to 200 C., whereupon the
volume of the molded body expands and the molded body hardens to a
thermoset.
20. A method as claimed in claim 19 wherein molding step (i) is
carried out by injection molding.
21. A method as claimed in claim 19 wherein molding step (i) is
carried out using a procedure selected from the group consisting of
extruding, casting, compression molding and stamping.
22. A method as claimed in claim 19 wherein said molded body
expands in volume by from 50 to 100% during step (iv).
23. A method as claimed in claim 19 wherein the temperature in step
(i) is from 70.degree. C. to 90.degree. C.
24. A method as claimed in claim 19 wherein the temperature in step
(iv) is from 130.degree. C. to 180.degree. C.
25. A method as claimed in claim 19 wherein the molded body is
softened by heating when applying the molded body to the
substrate.
26. A thermosetting, thermally-expandable molded body which is
dimensionally stable and not tacky at room temperature comprising:
(a) at least one liquid epoxy resin which is a liquid polyglycidyl
ether of a polyphenol and which has an epoxy equivalent weight of
150 to 480; (b) at least one solid epoxy resin which is a solid
polyglycidyl ether of a polyphenol and which has a melting point of
from 45.degree. C. to 90.degree. C.; (c) at least one reactive
resin conferring flexibility selected from the group consisting of
rubber-modified epoxy resins, polyurethane-modified epoxy resins,
adducts of amino-terminated polyoxyalkylenes and polyepoxides,
adducts of polymeric fatty acids and epichlorohydrin, glycidol, or
diglycidyl ethers of bisphenol A, adducts of polyether polyols with
epoxy resins, polysulfide-modified epoxy resins,
polymercaptan-modified epoxy resins and mixtures thereof: (d) at
least one latent hardener or accelerator selected from the group
consisting of guanidines, substituted guanidines, substituted
ureas, melamine resins, guanamine derivatives, cyclic tertiary
amines, aromatic amines, imidazole derivatives, and mixtures
thereof; (e) at least one expanding agent selected from the group
consisting of azo compounds, hydrazides, and expandable hollow
plastic microspheres; and (f) at least one light weight filler
selected from the group consisting of hollow glass microspheres,
flue ash, hollow plastic spheres, hollow ceramic spheres, organic
lightweight fillers of natural origin, and mixtures thereof.
27. A molded body as claimed in claim 26 additionally comprising
fibers selected from the group consisting of aramide fibers, carbon
fibers, glass fibers, polyamide fibers, polyethylene fibers,
polyester fibers and mixtures thereof.
28. A thermosetting, thermally-expandable molded body which is
dimensionally stable and not tacky at room temperature comprising:
(a) at leat one liquid epoxy resin obtained by reaction of
bisphenol A and epichlorohydrin and having an epoxy equivalent
weight of from 182 to 350; (b) at least one solid epoxy resin
obtained by reaction of bisphenol A and epichlorohydrin and having
a melting point from 50.degree. C. to 80.degree. C. and an epoxy
equivalent weight of from 450 to 900; (c) at least one reactive
resin conferring flexibility selected from the reaction products of
polymeric fatty acids with diglycidyl ethers of bisphenol A; (d) at
least one latent hardener or accelerator selected from substituted
guanidines; (e) expandable plastic microspheres; and (f) hollow
glass microspheres.
29. A molded body as claimed in claim 28 additionally comprising
polyaramide fibers selected from the group consisting of
polyaramide fibers, polyester fibers, and mixtures thereof.
30. A method of rigidifying and/or reinforcing a metal component,
said method comprising applying a molded body which is non-tacky
and dimensionally stable at room temperature and comprised of (a)
at least one solid reactive resin selected from the group
consisting of (i) solid polyglycidyl ethers of polyphenols,
polyalcohols, and diamines, (ii) solid polyglycidyl esters of
polycarboxylic acids, and mixtures thereof; (b) at least one liquid
reactive resin selected from the group consisting of (i) liquid
polyglycidyl ethers of polyphenols, polyalcohols, and diamines,
(ii) liquid polyglycidyl esters of polycarboxylic acids, and
mixtures thereof; (c) at least one reactive resin conferring
flexibility selected from the group consisting of rubber-modified
epoxy resins, polyurethane-modified epoxy resins, adducts of
amino-terminated polyoxyalkylenes and polyepoxides, adducts of
polymeric fatty acids and epichlorohydrin, glycidol, or diglycidyl
ethers of bisphenol A, adducts of polyether polyols with epoxy
resins, polymercaptan-modified epoxy resins, polysulfide-modified
epoxy resins, and mixtures thereof; (d) at least one additive
selected from the group consisting of hardeners and accelerators;
and (e) at least one expanding agent, to said metal component and
heating said molded body to a temperature effective to expand said
molded body in volume and to harden said molded body to a
thermoset.
31. A method claimed in claim 30 wherein said molded body is
additionally comprised of fibers.
Description
This application claims priority from International application
PCT/EP00/01474, filed Feb. 23, 2000, and German application DE
19909270.2, filed Mar. 3, 1999.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention pertains to reduced tack foamable compositions based
on epoxy resins. More specifically, particular combinations of
epoxy resins containing solid epoxy resins are utilized to obtain
putties which are sufficiently low in surface tackiness to be
readily handled, yet are pliable enough to be shaped to conform to
non-planar surfaces.
2. Discussion of the Related Art
It is known that a number of industries, e.g., the automobile
industry, require parts that are both strong and light-weight. One
attempt to achieve this balance between strength and minimal weight
provides for hollow metal parts. However, hollow metal parts are
easily distorted. Accordingly, it is also known that the presence
of structural foam in the cavities of the hollow parts can improve
the strength and stiffness of such parts.
Generally, such foams comprise a thermosettable resin such as an
epoxy resin, a blowing agent and a filler. Preferably, these foams
have a density of about 20-40 lb/ft.sup.3 (about 0.30 to about 0.65
g/cc) and are able to withstand heat in excess of 175.degree. C.,
more preferably in excess of 200.degree. C. Optional ingredients
include accelerators, curing agents, processing aids, stabilizers,
colorants, and UV absorbers.
Specific formulas for structural foam vary widely and are widely
found. For example, U.S. Pat. No. 5,575,526 teaches several
resin-based structural foams including Formula 2, which contains
54.5% EPON 828 epoxy resin, 7.5% HALOXY 62 epoxy diluent, 6.1% DER
732 flexible epoxy, 2.0% EXPANCEL 551DU blowing agent, 8.8% MICROS
microspheres, 17.7% 3M K20 microspheres and 3.4% DI-CY
dicyandiamide curing agent. U.S. Pat. No. 5,755,486 discloses
thermally expandable resin-based materials containing, for example,
epoxy resin, acrylonitrile-butadiene rubber, calcium carbonate,
carbon black, fumed silica, glass spheres, curing agent,
accelerator, and blowing agent. Structural foams such as, e.g.,
Terocore.RTM. (a product of Henkel Surface Technologies), are now
used in a variety of industries.
One recurrent problem with many of the structural foam formulations
of this type that have been developed to date has been their
relatively high degree of tack.
In many of the end-use applications in which structural foams are
employed, a desired quantity of the structural foam in its uncured,
unfoamed state must be placed on or near the surface of a metal
part. Said surface may be somewhat difficult to access due to its
proximity to other surfaces, thus often requiring the foamable
composition to be applied manually. It will typically be desirable
to have the foamable composition be sufficiently pliable or
dough-like in consistency so that it may be easily shaped and
otherwise manipulated to approximately follow the contours of the
surface to which it is being applied.
Certain known structural foam formulations provide excellent
strength and other physical properties when foamed and cured, yet
are somewhat difficult to work with due to their pronounced
"stickiness" prior to curing. The uncured formulation thus often
does not separate cleanly from the hands or gloves of the operator
who is applying the formulation to the structural member or the
like into which the formulation is to be incorporated as a
composite. A similar problem exists where tools or other machinery
are utilized in the application of the foamable formulation.
Residue from the uncured formulation consequently tends to build up
on the application instruments being used, requiring periodic
disposal or cleaning. Besides wasting a portion of the foamable
formulation, productivity suffers due to the cleaning time
required. It would therefore be very desirable to modify the
properties of such foamable compositions in order to lower the
surface tackiness, without significantly affecting either the
pliability of the composition or its performance when foamed and
cured.
SUMMARY OF THE INVENTION
It has now been surprisingly discovered that the excessive
tackiness problems encountered in previously known structural foam
formulations based on liquid and/or semi-solid epoxy resins may be
effectively alleviated through the use of solid epoxy resins. The
dough or putty thereby obtained may stil be easily formed into any
desired configuration, yet leaves little or no residue on the
instruments (e.g., hands, gloves, tools) used for such
manipulation. Reduced tack foamable compositions thus are provided
which comprise one or more base epoxy resins selected from the
group consisting of liquid epoxy resins and semi-solid epoxy
resins, one or more blowing agents, and one or more curatives, and
an amount of one or more solid epoxy resins effective to reduce the
surface tackiness of the foamable composition as compared to the
surface tackiness of an analogeous foamable composition which does
not contain any solid epoxy resin. Such compositions when foamed
and cured furnish structural foams having excellent physical
properties, including high strength and heat resistance.
DETAILED DESCRIPTION OF THE INVENTION
Preferred foam formulations contain about 35 weight percent to
about 85 weight percent total of epoxy resins, about 5 weight
percent to about 60 weight percent of fillers (preferably,
including about 5 weight percent to about 50 weight percent hollow
glass microspheres), about 0.1 weight percent to about 5 weight
percent of one or more blowing agents, and about 0.1 weight percent
to about 10 weight percent of one or more curatives. The foamable
composition may also contain varying amounts of other additives
such as blowing agent accelerators (activators), adhesion promoters
(coupling agents), toughening/flexibilizing agents,
thixotropic/rheological control agents, colorants and/or
stabilizers. It is particularly advantageous to select formulation
components which, when mixed together, provide a foamable dough of
putty-like consistency which can be readily molded or shaped into
any desired configuration prior to foaming and curing. At the same
time, the dough should not exhibit a significant degree of cold
flow. That is, the dough should essentially retain its shape over
an extended period of time at ambient temperatures.
DETAILED DESCRIPTION OF THE INVENTION
Selection of the epoxy resins to be utilized is critical to the
present invention. As a base epoxy resin, one or more liquid and/or
semi-solid epoxy resins are employed. One or more solid epoxy
resins are combined with the base epoxy resin to modify the surface
tack of the foamable composition thereby obtained, as will be
described in more detail hereinafter. Characterization herein of
the physical form of a particular epoxy resin (i.e., "liquid",
"semi-solid", "solid") is in reference to its form at approximately
room temperature (i.e., about 25.degree. C.). Semi-solid epoxy
resins are those epoxy resins which are neither completely solid
nor completely liquid at room temperature.
Generally speaking, epoxy resins are those thermosettable resins
having an average of more than one (preferably, about two or more)
epoxy groups per molecule.
Epoxy resins are well-known in the art and are described, for
example, in the chapter entitled "Epoxy Resins" in the Second
Edition of the Encyclopedia of Polymer Science and Engineering,
Volume 6, pp. 322-382 (1986). Exemplary epoxy resins include
polyglycidyl ethers obtained by reacting polyhydric phenols such as
bisphenol A, bisphenol F, bisphenol AD, catechol, or resorcinol, or
polyhydric aliphatic alcohols such as glycerin, sorbitol,
pentaerythritol, trime thylol propane and polyalkylene glycols with
haloepoxides such as epichlorohydrin; glycidylether esters obtained
by reacting hydroxycarboxylic acids such as p-hydroxybenzoic acid
or beta-hydroxy naphthoic acid with epichlorohydrin or the like;
polyglycidyl esters obtained by reacting polycarboxylic acids such
as phthalic acid, tetrahydrophthalic acid or terephthalic acid with
epichlorohydrin or the like; epoxidated phenolic-novolac resins
(sometimes also referred to as polyglycidyl ethers of phenolic
novolac compounds); epoxidated polyolefins; glycidylated
aminoalcohol compounds and aminophenol compounds, hydantoin
diepoxides and urethane-modified epoxy resins.
Preferably, both the base epoxy resin(s) and the solid epoxy
resin(s) are glycidyl ethers of polyhydric phenols (with bisphenol
A being a particularly preferred polyhydric phenol) containing an
average of about 2 epoxy groups per molecule. It is desirable to
use base epoxy resins having epoxide equivalent weights in the
range of from about 150 to about 350 (more preferably, about 170 to
about 300). The solid epoxy resins, on the other hand, preferably
have melting points in the range of from about 40.degree. C. to
about 150.degree. C. (more preferably, about 50.degree. C. to about
100.degree. C.) and epoxide equivalent weights in the range of from
about 350 to about 2000 (more preferably, about 375 to about 600).
Numerous epoxy resins meeting these requirements are available from
commercial sources. Representative commercial resins suitable for
use as the base epoxy resin molecule include, but are not limited
to, PEP 6134 (available from Peninsula Polymers) and EPON 834
(available from Shell Chemical). Representative commercial resins
suitable for use as the solid epoxy resin component include, but
are not limited to, ARALDITE CT 6060 (available from Ciba) and EPON
1001 (available from Shell Chemical).
Sufficient solid epoxy resin should be incorporated into the
foamable composition so as to impart the desired degree of surface
tack to said composition. The optimum surface tack will, of course,
vary somewhat depending upon the particular end-use application and
conditions under which the foamable composition is to be handled.
Generally speaking, however, it will be desirable to add an amount
of solid epoxy resin so as to obtain a dough which when manipulated
at a temperature of from about 20.degree. C. to about 40.degree. C.
does not leave any residue on the instruments being used to
manipulate the dough. At the same time, however, the use of
excessive quantities of solid epoxy resin should be avoided as the
pliability of the dough may be adversely affected (i.e., the dough
may become too stiff to be readily formed into a desired shape
prior to foaming and curing). Additionally, some degree of residual
surface tack is often desirable in order that the foamable dough
when placed in contact with a substrate surface does not readily
separate from said surface while the substrate is being further
handled prior to curing and foaming. Ideally, the surface tack is
adjusted by varying the base epoxy resin: solid epoxy resin ratio
to obtain a dough which adheres to a metal surface when pressed
into place, yet is capable of being released from said surface
without leaving any residue. The types and amounts of the other
components of the foamable composition will of course also
influence the ratio of base to solid epoxy resin used. For example,
the presence of relatively high concentrations of solid fillers may
reduce the quantity of solid epoxy resin necessary to achieve a
satisfactory tack level. If diluents are incorporated in the
foamable composition, then larger amounts of solid epoxy resin may
have to be used than would be the case in the absence of the
diluents.
The optimum proportions of base epoxy resin(s) to solid epoxy
resin(s) will depend upon the particular end-use contemplated as
well as the physical and chemical characteristics of the individual
resins. For example, if an epoxy resin which is fully liquid at
room temperature is selected for use as the base epoxy resin, a
somewhat larger amount of a solid epoxy will need to be added to
achieve a given level of surface tack than would be the case if a
semi-solid epoxy resin were instead utilized as the base epoxy
resin. Thus, generally speaking, greater quantities of a given
solid epoxy resin will need to be used as the melting
(solidification) point of the base epoxy resin decreases. If the
solid epoxy resin has a relatively high melting point, then
typically a smaller amount will need to be added as compared to a
solid epoxy resin having a relatively low melting point.
In general, it has been found that a weight ratio of base epoxy
resins to solid epoxy resins in the range of from about 10:1 to
about 1:5 will often be suitable, subject to the considerations
discussed in detail hereinabove.
The hardening of the thermosettable epoxy utilized in the present
invention may be accomplished by the addition of any chemical
materials known in the art for curing such resins. Such materials
are referred to herein as "curatives", but also include the
substances known to workers in the field as curing agents,
hardeners, activators, catalysts or accelerators. While certain
curatives promote epoxy resin curing by catalytic action, others
participate directly in the invention of the resin and are
incorporated into the thermoset polymeric network formed by
condensation, chain-extension and/or crosslinking of the epoxy
resins.
It is particularly desirable to employ at least one curative which
is a nitrogen-containing compound. Such curatives (along with other
curatives useful for hardening epoxy resins) are described in the
chapter in the Encyclopedia of Polymer Science and Engineering
referenced herein. Suitable nitrogen-containing compounds useful as
curatives include, amino compounds, amine salts, and quaternary
ammonium compounds. Particularly preferred types of
nitrogen-containing compounds include amine-epoxy adducts and
guanidines. In one desirable embodiment of the invention, two or
more different types of these nitrogen-containing compounds are
used in combination.
Amine-epoxy adducts are well-known in the art and are described,
for example, in U.S. Pat. Nos. 3,756,984, 4,066,625, 4,268,656,
4,360,649, 4,542,202, 4,546,155, 5,134,239, 5,407,978, 5,543,486,
5,548,058, 5,430,112, 5,464,910, 5,439,977, 5,717,011, 5,733,954,
5,789,498, 5,798,399 and 5,801,218, each of which is incorporated
herein by reference in its entirety.
Such amine-epoxy adducts are the products of the reaction between
one or more amine compounds and one or more epoxy compounds.
Carboxylic acid anhydrides, carboxylic acids, phenolic novolac
resins, water, metal salts and the like may also be utilized as
additional reactants in the preparation of the amine-epoxy adduct
or to further modify the adduct once the amine and epoxy have been
reacted. Preferably, the adduct is a solid which is insoluble in
the epoxy resin component of the present invention at room
temperature, but which becomes soluble and functions as an
accelerator to increase the cure rate upon heating. While any type
of amine could be used (with heterocyclic amines and/or amines
containing at least one secondary nitrogen atom being preferred),
imidazole compounds are particularly preferred. Illustrative
imidazoles include 2-methyl imidazole, 2,4-dimethyl imidazole,
2-ethyl-4-methyl imidazole, 2-phenyl imidazole and the like. Other
suitable amines include, but are not limited to, piperazines,
piperidines, pyrazoles, purines, and triazoles. Any kind of epoxy
compound can be employed as the other starting material for the
adduct, including monofunctional, bifunctional, and polyfunctional
epoxy compounds such as those described previously with regard to
the epoxy resin component. Suitable amine-epoxy adducts are
available from commercial sources such as Ajinomoto, Inc., Shell,
Pacific Anchor Chemical Company, and the Asahi Chemical Industry
Company Limited. The products sold by Ajinomoto under the trademark
"AJICURE PN40" and "AJICURE-PN-23" are especially preferred for use
in the present invention.
Dicyandiamide (sold commercially by Air Products under the
trademark "DICY") is also a particularly preferred curative,
although other guanidine compounds may also be utilized. The
curative system may also compare one or more ureas, either above or
in combination with other types of curatives (especially guanidines
such as dicyandiamide). Suitable ureas include alkyl and aryl
substituted ureas. Many such ureas are available commercially, for
example, N,N'-dimethyl urea, which is sold under the trademark
"AMICURE UR" by Air Products. Imidazoles such as 2-ethy-4methyl
imidazole may also be used as curatives.
The curative system (i.e., the specific curatives and the amounts
of such curatives) should be selected such that it does not
catalyze curing of the foamable composition to any significant
extent under typical storage conditions over an extended period of
time. Preferably, the components of the curative system are
adjusted such that the foamable composition retains a workable
consistency (in one embodiment of the invention, a consistency
resembling that of a pliable dough or putty) for more than two
weeks in storage at 130 F (54.degree. C.) and does not expand in
volume or decrease in specific gravity under such conditions to an
unacceptable extent, yet foams and cures within 10 minutes upon
being heated at 150.degree. C. or higher to provide a foam
comparable in properties to those of a foam obtained from a freshly
prepared foamable composition.
Selection of the blowing agent or blowing agents to be used in the
present invention is not believed to be particularly critical,
although chemical blowing agents in general are preferred over
physical blowing agents. Any of the chemical blowing agents known
in the art may be employed, with azodicarbonamide (also sometimes
referred to as 1,1'-azobisformamide, AZDC, or ADC) and sulfonyl
hydrazides providing particular good performance. Azodicarbonamide
is available from a number of commercial sources; for example, it
is sold under the trademark UNICELL by Doug Jin Chemical of South
Korea and under the CELOGEN trademark by Uniroyal Chemical.
"Activated" or "modified" forms of azodiacarbonamide may be used to
advantage. In some formulations, it may be desirable to also use a
blowing agent accelerator (activator) such as a urea so as to lower
the temperature at which release of the gas from the blowing agent
takes place. Typically, about 0.05% to about 2% blowing agent
accelerator based on the weight of the foamable composition is
employed, although the optimum amount will, of course, vary
depending upon the accelerator selected, the amount of blowing
agent, cure temperature and other variables. Excess accelerator
should not be present in the foamable composition, however, since
the storage stability may be undesirably compromised.
It will be especially desirable to include one or more glass
fillers in the foamable composition, as such fillers have been
found to impart useful characteristics to the resulting foam
(especially where it is to be used to reinforce a structural
member). For example, hollow glass microspheres may be added to
reduce the density of the foam and thus the overall weight of the
reinforced structural member while maintaining good stiffness and
strength. Commercially available glass microspheres (sometimes also
referred to as glass microballoons or microbubbles) include the
materials sold by Minnesota Mining and Manufacturing under the
trademark SCOTCHLITE, with suitable grades including those sold
under the designations B38, C15, K20 and VS 5500. The glass
microspheres preferably have diameters in the range of from about 5
to about 200 micrometers (preferably, less than about 70
micrometers). The crush strength of the hollow glass microspheres
may be selected in accordance with the desired characteristics of
the cured thermoset foam or reinforced structural member containing
said foam. Microspheres having a crush strength in excess of 500
psi are typically employed, however. Glass fiber is another
preferred type of glass filler, since it helps increase the
strength and stiffness of the resulting foam. The glass fiber may
be chopped, milled or in other physical forms.
Other types of fillers (which includes substances capable of
functioning as thixotropic or rheological control agents) may also
be optionally present in the foamable composition. Any of the
conventional inorganic or organic fillers known in the
thermosettable resin art may be used including, for example, fibers
other than glass fibers (e.g. wollastinite fibers, carbon fibers,
ceramic fibers, aramid fibers), silica (including fumed or
pyrogenic silica, which may also function as a thixotropic or
rheological control agent), calcium carbonate (including coated
and/or precipitated calcium carbonate, which may also act as a
thixotropic or rheological control agent, especially when it is in
the form of fine particles), alumina, clays, sand, metals (e.g.,
aluminum powder), microspheres other than glass microspheres
(including thermoplastic resin, ceramic and carbon microspheres,
which may be solid or hollow, expanded or expandable), and any of
the other organic or inorganic fillers known in the epoxy resin
field. The quantity of thixotropic agent(s) is desirably adjusted
so as to provide a dough which does not exhibit any tendency to
flow at room temperature.
Other optional components include diluents (reactive or
non-reactive) such as glycidyl ethers, glycidyl esters, acrylics,
solvents, and plasticizers, toughening agents and flexibilizers
(e.g., aliphatic diepoxides, polyaminoamides, liquid polysulfide
polymers, rubbers including liquid nitrile rubbers such as
butadiene-acrylonitrile copolymers, which may be functionalized
with carboxyl groups, amine groups or the like), adhesion promoters
(also known as wetting or coupling agents; e.g., silanes,
titanates, zirconates), colorants (e.g., dyes and pigments such as
carbon black), stabilizers (e.g., antioxidants, UV stabilizers),
and the like.
The formulations of the present invention preferably contain the
above-discussed components in the following amounts (expressed as a
percentage of the total weight of the foamable composition).
Component Preferred More Preferred Total Epoxy Resin(s) about 35-85
about 40-70 Base Epoxy Resin(s) about 5-80 about 10-60 Solid Epoxy
Resin(s) about 5-80 about 10-60 Blowing Agent(s) about 0.1-5 about
0.5-3 Curative(s) about 0.1-10 about 1-8 Filler(s) about 5-60 about
20-45 Adhesion Promoter(s) up to about 2 about 0.001-0.5
Colorant(s) up to about 2 about 0.01-1 Toughening/Flexibilizing
Agent(s) up to about 15 about 0.5-10 Blowing Agent Accelerator(s)
up to about 3 about 0.05-2 Stabilizer(s) up to about 2 about
0.01-1
Preferably, epoxy resin is present in an amount which is greater
than the amount of any of the other components in the foamable
composition.
The above-described ingredients may simply be combined and mixed to
form the foamable composition using any of the processing methods
known in the epoxy resin art. It may be desirable to pre-mix the
individual epoxy resins (i.e., the base epoxy resin(s) and solid
epoxy resin(s)) before combining with the other components of the
formulation.
The preferred finished product preferably has the consistency of
dough for easier handling. The dough may be shaped by extrusion, by
hand, or by cutting means into any desired configuration, thickness
or size. For example, the dough may be extruded to a wide, flat
continuous ribbon which can then be cut to a desired length and
applied to the surface of a solid article, being conformed to
follow the contours of said surface. The dough can then be cured
and foamed by heating, preferably at a temperature of at least
about 250.degree. F. (about 120.degree. C.), more preferably to at
least about 300.degree. F. (about 150.degree. C.). Preferably, it
is placed on or near the surface of a solid article comprised of,
for example, metal or a thermoset or thermoplastic polymer such
that a composite of the structural foam adhered to said surface is
created upon foaming and curing. The foamable compositions of this
invention are also useful for forming laminates, wherein the
foamable composition is sandwiched between layers of different
substrates (metal or plastic sheets or films, for example)
Alternatively, of course, the dough can be placed in a suitable
container or vessel for storage until the use of the foamable
composition is desired.
The foamable compositions of the present invention may be utilized
in any end-use application where a relatively light-weight, yet
strong, thermoset foam is needed. However, the foamable
compositions are especially useful in the production of automobiles
and other vehicles to maintain or increase the strength of
structural members such as rockers, pillars, radiator support
beams, doors, reinforcing beams, and the like. The use of
structural foams in such applications is described, for example, in
U.S. Pat. Nos. 4,901,500; 4,908,930; 4,751,249; 4,978,562;
4,995,545; 5,124,186; 5,575,526; 5,755,486; 5,884,960; 5,888,600;
4,923,902; 4,922,596; 4,861,097; 4,732,806; 4,695,343; and
4,610,836 and European Patent Publication Nos. EP 0891918, EP
893331 and EP 0893332 and International Patent Publication Nos. WO
99/08854 (each of which is incorporated herein by reference in its
entirety).
EXAMPLES
Examples 1-10
Foamable compositions in accordance with the present invention were
prepared by combining the components listed in Table 1. The
relative proportions of base epoxy resin to solid epoxy resin were
varied to study the effect on surface tack of the resulting
dough.
In Examples 1-3, tack was effectively reduced to an acceptable
level but the degree of expansion observed upon heating and curing
was somewhat low. In Examples 4-6, the amount of calcium carbonate,
fumed silica and nitrile rubber were varied. Increasing the calcium
cabonate levels generally resulted in a harder cured foam, while
the degree of expansion was affected by the amount of fumed silica
and nitrile rubber present. Flexibility was improved by the
addition of nitrile rubber. Example 10 contained aluminum powder,
which was added as a filler for the purpose of conducting heat
through the foamable composition to allow for more even heat
distribution and appropriate expansion of the composition.
Examples 11-21
Examples 11-21 illustrate various embodiments of the present
invention wherein the ratio of base epoxy resin to solid epoxy
resin was varied and different curative systems, coupling agents
(adhesion promoters) and fillers evaluated.
To prepare the foamable dough of Example 11, the epoxy resins and
flexibilizing/toughening agent were combined and mixed at low speed
using a Ross double planetary mixer or Sigma blade mixer/extruder
having a bowl temperature of 130.degree. F. (54.degree. C.). The
calcium carbonate, fumed silica and colorant were thereafter added
and mixed 10 minutes until uniformly incorporated. One-half of the
hollow glass microspheres was added and mixed 10 minutes, following
by the remaining amount of hollow glass microspheres. After mixing
another 10 minutes, the remaining components were added and mixed
for 5 minutes, scraping down the sides of the mixer periodically. A
vacuum was then applied for 70 minutes to remove air from the dough
obtained.
TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex.
10 Component Identity Supplier Wt. % Wt. % Wt. % Wt. % Wt. % Wt. %
Wt. % Wt. % Wt. % Wt. % Base Epoxy Resins PEP 6134 Peninsula 45.96
37.34 28.73 43.09 38.50 40.25 40.72 37.82 37.53 36.75 Polymers
Solid Epoxy Resins CT 6060 Ciba 11.49 20.10 28.73 14.33 20.73 17.24
17.24 20.36 20.21 19.79 Curatives Dicyandiamide DICY G Air Products
4.33 4.33 4.33 4.33 4.46 4.33 4.38 4.38 4.33 4.26 Urea AJICURE UR
Air Products 1.29 1.29 1.29 1.29 1.33 1.29 1.31 1.31 1.30 1.27
Blowing Agent CELOGEN OT Uniroyal 0.71 0.71 0.71 -- -- -- -- -- --
-- CELOGEN Uniroyal -- -- -- 0.71 0.73 0.71 0.72 0.72 0.72 0.80 AZ
120 Fillers Calcium Carbonate ULTRA PFLEX Specialty 5.81 5.81 5.81
5.80 4.95 4.80 5.37 5.37 5.81 5.22 Chemicals Fumed Silica CAB-O-SIL
Cabot 3.55 3.55 3.55 3.55 3.66 3.55 4.05 4.05 4.27 3.94 T5720
Hollow Glass B-38 3M 22.40 22.40 22.40 22.41 22.07 22.41 21.48
21.48 21.32 20.88 Microspheres Aluminium Powder -- -- -- -- -- --
-- -- -- -- -- 2.71 Toughening/ NIPOL 1312 Zeon 4.33 4.33 4.33 4.33
3.43 4.33 4.37 4.38 4.35 4.26 Flexibilizing Agent Colorant MONARCH
120 Cabot 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 Uncured
Specific -- -- -- -- -- -- 0.77 0.815 -- -- Gravity Cured Specific
-- -- -- -- -- -- 0.51 0.523 -- 0.52 Gravity % Expansion -- -- --
-- -- -- 54 52 -- 60
TABLE 2 Ex. 11 Ex. 12 Ex. 13 Ex. 14 Ex. 15 Ex. 16 Ex. 17 Ex. 18 Ex.
19 Ex. 20 Ex. 21 Component Identity Supplier Wt. % Wt. % Wt. % Wt.
% Wt. % Wt. % Wt. % Wt. % Wt. % Wt. % Wt. % Base Epoxy PEP 6134
Peninsula 34.45 29.70 35.27 34.90 36.94 20.73 36.40 16.49 36.73
16.35 36.95 Resins Polymers Solid Epoxy CT 6060 Ciba 18.55 24.31
18.99 18.79 19.89 38.50 19.60 38.47 19.78 38.14 19.90 Resins
Curatives Dicyandiamide DICY CGNA Air 4.01 4.42 4.11 4.07 4.30 --
-- -- 4.28 -- 4.30 DICYANEX Products -- -- -- -- -- 4.49 4.24 4.16
-- 4.13 -- 200X Amine-Epoxy AJICURE Ajinomoto 1.01 1.13 1.04 1.03
1.09 1.13 1.07 1.05 1.08 1.04 1.09 Adduct PR-23 Amine JEFFAMINE
Texaco -- -- -- -- -- 4.49 4.24 4.16 0.59 0.85 -- D-2000 Blowing
CELOGEN OT Uniroyal 0.92 0.94 0.94 0.93 0.99 1.03 0.97 0.96 0.98
0.95 0.99 Agents CELOGEN Uniroyal 0.92 0.94 0.94 0.93 0.99 1.03
0.97 0.96 0.98 0.95 0.99 AZ 120 Fillers Calcium ULTRA 4.43 4.51
4.53 4.49 4.75 4.43 4.68 4.11 4.72 4.08 4.75 Carbonate PFLEX Fumed
Silica CAB-O-SIL Cabot 3.28 3.34 0.99 0.98 3.51 0.26 3.46 2.39 3.49
2.37 3.51 T5720 Hollow Glass B-38/VS 5500 3M 27.68 25.85 28.33
28.04 22.16 23.10 21.84 26.31 22.03 26.08 22.16 Micropheres
Wollastanite NYAD G -- -- -- 0.93 -- -- -- -- -- -- -- Aluminium --
-- -- -- -- -- 1.46 -- -- -- -- Powder Toughening/ NIPOL 1312 Zeon
4.00 4.07 4.09 4.05 4.28 4.46 4.22 4.14 4.26 4.11 4.28
Flexibilizing Agent Coupling KEN-REACT Kenrich 0.09 0.09 0.09 --
0.40.sup.1 0.10 0.39.sup.2 0.10 0.10 0.09 0.10 Agents KR-55 Petro-
chemicals A1120 Witco -- -- -- 0.09 -- -- -- 0.19 0.10 0.19 0.10
Colorants MONARCH Cabot 0.12 0.12 0.12 0.12 0.13 0.13 0.13 0.12
0.13 0.12 0.13 120 414 GREEN Akrochem -- -- -- -- -- -- -- -- 0.18
-- 0.18 (phthalo- cyamine) Blowing Agent BYK OT Uniroyal 0.53 0.59
0.54 0.54 0.57 0.59 0.56 0.55 0.57 0.55 0.57 Accelerator Uncured --
-- 0.725 0.710 0.79 -- 0.79 0.79 0.796 0.782 -- Specific Gravity
Cured -- -- 0.415 0.307 0.46 -- 0.48 0.47 0.477 0.485 -- Specific
Gravity % Expansion -- -- 75 130 71 -- 65 68 67 62 -- Lap Shear, --
-- -- -- 915- 510- 930- 723- 641(1) 897(1) -- psi (#samples) 984(3)
595(3) 958(3) 851(5) .sup.1 0.10 wt % KEN-REACT KR-55 titanate,
0.10 wt % KEN-REACT NZ37 zirconate, 0.20 wt % KEN-REACT 238M
titanate .sup.2 0.10 wt % KEN-REACT KR-55 titanate, 0.10 wt %
KEN-REACT NZ37 zirconate, 0.19 wt % KEN-REACT 238M titanate
* * * * *